PC87309VLJ datasheet(158/192 Pages) NSC

158 / 192 page

Mouse and Keyboard Controller (KBC) (Logical Devices 5 and 6)

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8.0

Mouse and Keyboard Controller

(KBC) (Logical Devices 5 and 6)

The Keyboard Controller (KBC) is a functionally indepen-

dent programmable device controller. It is implemented

physically as a single hardware module on the PC87309

multi-I/O chip and houses two separate logical devices: a

mouse controller (Logical Device 5) and a keyboard control-

ler (Logical Device 6).

The KBC accepts user input from the keyboard or mouse,

and transfers this input to the host PC via the common

PC87309-PC interface.

The KBC is functionally equivalent to the industry standard

8042A keyboard controller, which may serve as a detailed

technical reference for the KBC.

The KBC is delivered preprogrammed with customer-sup-

plied code. KBC firmware code is identical to 8042 code,

and to code of the keyboard controller of the PC87323VUL

chip. The PC87323VUL is a recommended development

platform for the KBC since it uses identical code and in-

cludes internal program RAM that enables software devel-

opment.

8.1

SYSTEM ARCHITECTURE

The KBC is a general purpose microcontroller, with an 8-bit

internal data bus. See FIGURE FIGURE 8-1 "KBC System

Functional Block Diagram". It includes these functional

blocks:

Serial Open-collector Drivers: Four open-collector bi-di-

rectional serial lines enable serial data exchange with

the external devices (keyboard and mouse) using the

PS/2 protocol.

Program ROM: 2 Kbytes of ROM store program machine

code in non-erasable memory. The code is copied to

this ROM during manufacture, from customer-supplied

code.

Data RAM: A 256-byte data RAM enables run-time inter-

nal data storage, and includes an 8-level stack and 16

8-bit registers.

Timer/Counter: An internal 8-bit timer/counter can count

external events or pre-divided system clock pulses. An

internal time-out interrupt may be generated by this de-

vice.

I/O Ports: Two 8-bit ports (Port 1 and Port 2) serve various

I/O functions. Some are for general purpose use, others

are utilized by the KBC firmware.

FIGURE 8-1. KBC System Functional Block Diagram

KBDAT

Interrupt Matrix

KBCLK MDAT MCLK

Program

ROM

2 K x 8

Data

RAM

256 x 8

(including

registers

and stack)

I/O Port 2

8-Bit

Serial Open-Collector

Drivers

8-Bit Timer

DBBOUT

DBBIN

STATUS

RD WR

P21-20

P27, P26, P23, P22

TEST1

TEST0

D7-0

Timer

8-Bit Internal Bus

Program

Address

IBF

I/O Interface

PC87309 Interface

I/O PORT 1

8-Bit

P11,10

P12

P24

P25

8-Bit

CPU

To PnP

or Counter

Overflow

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